Eric A. Roy
Apraxia involves a disruption in the performance of gestures, both transitive (with objects) and intransitive (without objects), and/or more complex sequential motor acts, such as putting a letter into an envelope. In examining this disorder we do not describe the traditional classifications (e.g., ideational, ideomotor, and limb-kinetic apraxias) as these are fully described in this volume and elsewhere ( Heilman, 1979; Roy, 1982). Rather, consideration is given to the types of errors observed and the four major views as to the nature of apraxia. Discussion then focuses on the work by Roy ( 1978, 1981, 1982, 1983) and others ( Luria, 1980), which considers that apraxia results from a disruption to a functional neurobehavioural system.
In performing actions errors may be observed in sequences of action or in single gestures. For movement sequences errors involve omissions, repetitions, misordering of movements in the sequence, a difficulty in terminating movements when required, and in coordinating the limbs in time and space. Errors involved in performing the movement elements which form the sequence have been described by Kimura and Archibald ( 1974) and Heilman ( 1979) as clumsiness. Movement loses its smoothness and becomes jerky and ataxic-like: fine finger control may be particularly affected ( Heilman, 1975).
With regard to single gestures movements may be performed in a clumsy, ataxic-like fashion; the movement may be misaligned in space so that it is in the wrong plane or, when using an implement (e.g., a saw), it may be grasped in a